It's solved. I just had to use the self-adjoint form.
Hi there. I have this exercise, which says:
Demonstrate that:
has a polynomial solution for some λ values.
Indicate the orthogonality relation between polynomials, the fundamental interval, and the weight function.
So I thought I should solve this using Frobenius method. I have one singular point at x=0, which is regular. I assumed a solution of the form:
And then replacing in the diff. eq. I get:
Therefore r=0.
Then replacing r=0, and changing the index for the first summation, with m=n-1, n=m+1:
And now calling m=n
So I have the recurrence relation:
Trying some terms:
I'm not sure what this gives, I tried this:
This is wrong, because the factorial in the numerator is only defined for positive values of (n-1-λ), and if n=1 I get -λ!, which wouldn't work for a_1, unless λ=0, which gives the trivial solution. But I think it works for n>1.
So I tried in a different fashion:
And now I called:
I think this is wrong too, because for example, n=1 gives which doesn't fit.
Then λ-n can't be a negative integer, and the polynomials would be given by:
Anyway, I took the diff. eq. into it's self adjoint form:
I actually think that I didn't have to get this explicit solution. To demonstrate what the problem asks I think I should take the equation to the self adjoint form.
Multiplying by
I get:
This is the self adjoint form for my differential equation. Then the weight function is given by:
I don't know how to get the fundamental interval.
Would it be ok just to work it in this last form, with out finding an explicit solution?
How can I get the fundamental interval?